This invention is directed to a hydraulic dredge cutter head which is mounted on a dredge ladder in a novel manner and to a method of using this uniquely mounted cutter head to dredge in a most efficient and productive manner.
Cutter heads which are pivotally mounted on the end of a dredge ladder are known in the art, a good example of which is the cutter head shown in Netherlands Patent No. 298,911 to Glas. In the prior art, such cutter heads are mounted on stub arms which are pivotally attached to the end of a dredge ladder. Because of the length of such a stub arm, even a small angular rotation of the cutter head causes a relatively large movement of the cutter head along an arcuate path. This arcuate movement reduces the efficiency of production of such a cutter head because every time the cutter head is pivoted relative to the end of the ladder, either to maintain the cutter head horizontally, as suggested by some of the prior art, or to cut to a level bottom, as suggested by other of the prior art, the effective arc of the ladder and cutter head is shortened and the cutter head is backed out of the swath which is being cut. In this manner, the amount of material removed during a subsequent arcuate swing of the ladder and cutter head is reduced.
The most efficient digging swath is maintained when the cutter head is a longitudinal extension of the ladder because this arrangement provides the widest digging swath for the cutting head and thus the greatest removal of material during a cutting arc. However, it is desirable at times to dig to a flat bottom without the additional expense and time of overdigging and this is best accomplished by using a pivotally mounted cutter head. Using the novel mounting of the cutter head of my invention, it is possible to tilt the cutter head to a level bottom cutting position without reducing the effective cutting swath of the fully extended cutter head.
Consequently, a purpose of this invention is to provide a tiltable cutter head for a hydraulic dredge which cutter head moves only a small arcuate distance when it is tilted through a relatively large angle relative to the dredge ladder.
Another purpose of this invention is to provide a rotatable cutter head for a hydraulic dredge which is tiltably mounted on the end of a ladder in such a manner that the cutter head is not pulled out of the normal cutting swath of the cutter head when it is tilted from its aligned position with the ladder.
Another purpose of this invention is a pivotable mounting for a cutter head which allows the cutter head to be pivoted from alignment with the longitudinal axis of a ladder to a level bottom digging position without reducing the effective cutting swath of the cutter head.
Another purpose of this invention is a method of dredging to a level flat bottom using a tiltable cutter head in which the cutter head is maintained aligned with the longitudinal axis of the ladder during all of the cutting arcs through a bank of material except the last cutting arc above the bottom of the bank of material at which point it is tilted so its blades are parallel to the desired level bottom.